Temperature Dependence of XANES Spectra for ATiO3, A2TiO4 and TiO2 Compounds with Structural Phase Transitions

2007 ◽  
Author(s):  
Takafumi Hashimoto ◽  
Akira Yoshiasa ◽  
Maki Okube ◽  
Hiroki Okudera ◽  
Akihiko Nakatsuka
Keyword(s):  
Phase Transitions ◽  
Temperature Dependence ◽  
Structural Phase ◽  
Structural Phase Transitions

scholarly journals NQR and DSC Studies on Structural Phase Transitions and Lattice Stability in Some Tetrabromozincate(II) Compounds A2ZnBr4

2002 ◽  
Vol 57 (6-7) ◽  
pp. 425-430 ◽  
Author(s):  
Keizo Horiuchi ◽  
Hideta Ishihara ◽  
Naoko Hatano ◽  
Syuntaroh Okamoto ◽  
Tohru Gushiken
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Temperature Dependence ◽  
Single Phase ◽  
Structural Phase ◽  
Lattice Stability ◽  
Structural Phase Transitions ◽  
Melting Points ◽  
Dsc Studies ◽  
Disorder Type

The temperature dependence of 81Br NQR frequencies in some tetrabromozincate(II) compounds, pyridinium tetrabromozincate(II) (pyH)2ZnBr4, 4-picolinium tetrabromozincate(II) (4- piH)2ZnBr4, 2,6-lutidinium tetrabromozincate(II) (2,6-luH)2ZnBr4 and guanidinium tetrabromozincate( II) (guH)2ZnBr4,weremeasured between 77Kand temperatureswhere signals faded out.All compounds exhibited four NQR signals over the whole temperature range investigated. Moreover, DSC was measured between about 130 K and melting points. (4-piH)2ZnBr4 and (guH)2ZnBr4 showed no structural phase transition, while (pyH)2ZnBr4 and (2,6-luH)2ZnBr4 showed a single phase transition. The values of transition entropies obtained suggest that these transitions are of the order-disorder type. The nature of these transitions and the lattice stability in the present compounds were discussed

Evidence for precursor clusters associated with structural phase transitions in antifluorite crystals

1982 ◽  
Vol 60 (4) ◽  
pp. 397-398 ◽  
Author(s):  
Robin L. Armstrong ◽  
Marie D'Iorio ◽  
Maximo E. Ramia
Keyword(s):  
Phase Transitions ◽  
Temperature Dependence ◽  
Structural Phase ◽  
Indirect Evidence ◽  
Cubic Phase ◽  
Structural Phase Transitions ◽  
Type Phase ◽  
Symmetry Phase ◽  
Nuclear Quadrupole ◽  
Low Symmetry

Measurements of the temperature dependence of the intensities of the halogen nuclear quadrupole resonances in K2PtBr6 and K2ReCl6, in the cubic phase are reported. These results provide indirect evidence for the formation of dynamic clusters of the low symmetry phase as a precursor to the occurrence of rotative type phase transitions to tetragonal structures in these crystals.

Iodine NQR and Phase Transitions in [N(CH3)4]2 ZnI4

1990 ◽  
Vol 45 (3-4) ◽  
pp. 349-352 ◽  
Author(s):  
J. Pirnat ◽  
J. Lužnik ◽  
Z. Trontelj
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
High Temperature ◽  
Temperature Dependence ◽  
General Formula ◽  
Structural Phase ◽  
Structural Phase Transitions ◽  
Space Group ◽  
Crystal Space ◽  
Group D

Abstract Using a superregenerative NQR spectrometer, the temperature dependence of 127I NQR spectra in [N(CH3)4]2ZnI4 was measured between 167 and 335 K. The measurements confirm two known structural phase transitions at 219 and 257.5 K. The correspondence between the distinct regions of iodine NQR spectra and the crystal structure is discussed. The relation of [N(CH3)4]2ZnI4 to the incommensurate family with the general formula X2YZ4 and the high temperature (paraphase) crystal space group D162h (Pmcn) is studied.

Successive Phase Transitions in Potassium Hexachloroselenate(IV) Revealed by 35Cl NQR

1996 ◽  
Vol 51 (5-6) ◽  
pp. 705-709 ◽  
Author(s):  
Tetsuo Asaji ◽  
Masaki Ohkawa ◽  
Takehiko Chiba ◽  
Makoto Kaga
Keyword(s):  
Phase Transitions ◽  
Temperature Dependence ◽  
Structural Phase ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Structural Phase Transitions ◽  
Spin Lattice ◽  
35Cl Nqr ◽  
Successive Phase

Abstract K2SeCl6 undergoes structural phase transitions of first order at 35 K, 65 K, and 79 K. The temperature dependence of the 35Cl NQR spin-lattice relaxation time suggests that the phase transitions at 65 K and 79 K are displacive ones associated with a resonant soft mode. The presence of a precursor cluster is suggested by the temperature dependence of the signal intensity above 79 K.

Phonons and magnons under the sequential structural phase transitions in La2NiO4

1991 ◽  
Vol 185-189 ◽  
pp. 895-896 ◽  
Author(s):  
S. Sugai ◽  
S. Hosoya ◽  
T. Kajitani ◽  
T. Fukuda ◽  
S. Onodera
Keyword(s):  
Phase Transitions ◽  
Structural Phase ◽  
Structural Phase Transitions
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